The embodiments of the present invention relate to an image reading apparatus such as a document size reading apparatus and an image density detecting apparatus for a copying machine in which a solid state pick-up device receives light reflected from the image on a document.
A CCD line sensor is most widely used as the solid state pick-up device of an image reading apparatus. The light source of the image reading apparatus is normally a halogen lamp. For the CCD line sensor to read an image, it is necessary to control the quantity of light emitted from the light source according to the density of the image. For this reason, the conventional image reading apparatus is not capable of accurately reading a manuscript image.